<?php

/**
 * @file
 * User session handling functions.
 *
 * The user-level session storage handlers:
 * - _drupal_session_open()
 * - _drupal_session_close()
 * - _drupal_session_read()
 * - _drupal_session_write()
 * - _drupal_session_destroy()
 * - _drupal_session_garbage_collection()
 * are assigned by session_set_save_handler() in bootstrap.inc and are called
 * automatically by PHP. These functions should not be called directly. Session
 * data should instead be accessed via the $_SESSION superglobal.
 */

/**
 * Session handler assigned by session_set_save_handler().
 *
 * This function is used to handle any initialization, such as file paths or
 * database connections, that is needed before accessing session data. Drupal
 * does not need to initialize anything in this function.
 *
 * This function should not be called directly.
 *
 * @return
 *   This function will always return TRUE.
 */
function _drupal_session_open() {
	return TRUE;
}

/**
 * Session handler assigned by session_set_save_handler().
 *
 * This function is used to close the current session. Because Drupal stores
 * session data in the database immediately on write, this function does
 * not need to do anything.
 *
 * This function should not be called directly.
 *
 * @return
 *   This function will always return TRUE.
 */
function _drupal_session_close() {
	return TRUE;
}

/**
 * Reads an entire session from the database (internal use only).
 *
 * Also initializes the $user object for the user associated with the session.
 * This function is registered with session_set_save_handler() to support
 * database-backed sessions. It is called on every page load when PHP sets
 * up the $_SESSION superglobal.
 *
 * This function is an internal function and must not be called directly.
 * Doing so may result in logging out the current user, corrupting session data
 * or other unexpected behavior. Session data must always be accessed via the
 * $_SESSION superglobal.
 *
 * @param $sid
 *   The session ID of the session to retrieve.
 *
 * @return
 *   The user's session, or an empty string if no session exists.
 */
function _drupal_session_read($sid) {
	global $user, $is_https;

	// Write and Close handlers are called after destructing objects
	// since PHP 5.0.5.
	// Thus destructors can use sessions but session handler can't use objects.
	// So we are moving session closure before destructing objects.
	drupal_register_shutdown_function('session_write_close');

	// Handle the case of first time visitors and clients that don't store
	// cookies (eg. web crawlers).
	$insecure_session_name = substr(session_name(), 1);
	if (!isset($_COOKIE[session_name()]) && !isset($_COOKIE[$insecure_session_name])) {
		$user = drupal_anonymous_user();
		return '';
	}

	// Otherwise, if the session is still active, we have a record of the
	// client's session in the database. If it's HTTPS then we are either have
	// a HTTPS session or we are about to log in so we check the sessions table
	// for an anonymous session with the non-HTTPS-only cookie.
	if ($is_https) {
		$user = db_query("SELECT u.*, s.* FROM {users} u INNER JOIN {sessions} s ON u.uid = s.uid WHERE s.ssid = :ssid", array(':ssid' => $sid))->fetchObject();
		if (!$user) {
			if (isset($_COOKIE[$insecure_session_name])) {
				$user = db_query("SELECT u.*, s.* FROM {users} u INNER JOIN {sessions} s ON u.uid = s.uid WHERE s.sid = :sid AND s.uid = 0", array(
						':sid' => $_COOKIE[$insecure_session_name]))
						->fetchObject();
			}
		}
	}
	else {
		$user = db_query("SELECT u.*, s.* FROM {users} u INNER JOIN {sessions} s ON u.uid = s.uid WHERE s.sid = :sid", array(':sid' => $sid))->fetchObject();
	}

	// We found the client's session record and they are an authenticated,
	// active user.
	if ($user && $user->uid > 0 && $user->status == 1) {
		// This is done to unserialize the data member of $user.
		$user->data = unserialize($user->data);

		// Add roles element to $user.
		$user->roles = array();
		$user->roles[DRUPAL_AUTHENTICATED_RID] = 'authenticated user';
		$user->roles += db_query("SELECT r.rid, r.name FROM {role} r INNER JOIN {users_roles} ur ON ur.rid = r.rid WHERE ur.uid = :uid", array(':uid' => $user->uid))->fetchAllKeyed(0, 1);
	}
	elseif ($user) {
		// The user is anonymous or blocked. Only preserve two fields from the
		// {sessions} table.
		$account = drupal_anonymous_user();
		$account->session = $user->session;
		$account->timestamp = $user->timestamp;
		$user = $account;
	}
	else {
		// The session has expired.
		$user = drupal_anonymous_user();
		$user->session = '';
	}

	// Store the session that was read for comparison in _drupal_session_write().
	$last_read = &drupal_static('drupal_session_last_read');
	$last_read = array(
			'sid' => $sid,
			'value' => $user->session,
	);

	return $user->session;
}

/**
 * Writes an entire session to the database (internal use only).
 *
 * This function is registered with session_set_save_handler() to support
 * database-backed sessions.
 *
 * This function is an internal function and must not be called directly.
 * Doing so may result in corrupted session data or other unexpected behavior.
 * Session data must always be accessed via the $_SESSION superglobal.
 *
 * @param $sid
 *   The session ID of the session to write to.
 * @param $value
 *   Session data to write as a serialized string.
 *
 * @return
 *   Always returns TRUE.
 */
function _drupal_session_write($sid, $value) {
	global $user, $is_https;

	// The exception handler is not active at this point, so we need to do it
	// manually.
	try {
		if (!drupal_save_session()) {
			// We don't have anything to do if we are not allowed to save the session.
			return;
		}

		// Check whether $_SESSION has been changed in this request.
		$last_read = &drupal_static('drupal_session_last_read');
		$is_changed = !isset($last_read) || $last_read['sid'] != $sid || $last_read['value'] !== $value;

		// For performance reasons, do not update the sessions table, unless
		// $_SESSION has changed or more than 180 has passed since the last update.
		if ($is_changed || REQUEST_TIME - $user->timestamp > variable_get('session_write_interval', 180)) {
			// Either ssid or sid or both will be added from $key below.
			$fields = array(
					'uid' => $user->uid,
					'cache' => isset($user->cache) ? $user->cache : 0,
					'hostname' => ip_address(),
					'session' => $value,
					'timestamp' => REQUEST_TIME,
			);

			// Use the session ID as 'sid' and an empty string as 'ssid' by default.
			// _drupal_session_read() does not allow empty strings so that's a safe
			// default.
			$key = array('sid' => $sid, 'ssid' => '');
			// On HTTPS connections, use the session ID as both 'sid' and 'ssid'.
			if ($is_https) {
				$key['ssid'] = $sid;
				// The "secure pages" setting allows a site to simultaneously use both
				// secure and insecure session cookies. If enabled and both cookies are
				// presented then use both keys.
				if (variable_get('https', FALSE)) {
					$insecure_session_name = substr(session_name(), 1);
					if (isset($_COOKIE[$insecure_session_name])) {
						$key['sid'] = $_COOKIE[$insecure_session_name];
					}
				}
			}

			db_merge('sessions')
			->key($key)
			->fields($fields)
			->execute();
		}

		// Likewise, do not update access time more than once per 180 seconds.
		if ($user->uid && REQUEST_TIME - $user->access > variable_get('session_write_interval', 180)) {
			db_update('users')
			->fields(array(
					'access' => REQUEST_TIME
			))
			->condition('uid', $user->uid)
			->execute();
		}

		return TRUE;
	}
	catch (Exception $exception) {
		require_once DRUPAL_ROOT . '/includes/errors.inc';
		// If we are displaying errors, then do so with no possibility of a further
		// uncaught exception being thrown.
		if (error_displayable()) {
			print '<h1>Uncaught exception thrown in session handler.</h1>';
			print '<p>' . _drupal_render_exception_safe($exception) . '</p><hr />';
		}
		return FALSE;
	}
}

/**
 * Initializes the session handler, starting a session if needed.
 */
function drupal_session_initialize() {
	global $user, $is_https;

	session_set_save_handler('_drupal_session_open', '_drupal_session_close', '_drupal_session_read', '_drupal_session_write', '_drupal_session_destroy', '_drupal_session_garbage_collection');

	// We use !empty() in the following check to ensure that blank session IDs
	// are not valid.
	if (!empty($_COOKIE[session_name()]) || ($is_https && variable_get('https', FALSE) && !empty($_COOKIE[substr(session_name(), 1)]))) {
		// If a session cookie exists, initialize the session. Otherwise the
		// session is only started on demand in drupal_session_commit(), making
		// anonymous users not use a session cookie unless something is stored in
		// $_SESSION. This allows HTTP proxies to cache anonymous pageviews.
		drupal_session_start();
		if (!empty($user->uid) || !empty($_SESSION)) {
			drupal_page_is_cacheable(FALSE);
		}
	}
	else {
		// Set a session identifier for this request. This is necessary because
		// we lazily start sessions at the end of this request, and some
		// processes (like drupal_get_token()) needs to know the future
		// session ID in advance.
		$user = drupal_anonymous_user();
		// Less random sessions (which are much faster to generate) are used for
		// anonymous users than are generated in drupal_session_regenerate() when
		// a user becomes authenticated.
		session_id(drupal_hash_base64(uniqid(mt_rand(), TRUE)));
	}
	date_default_timezone_set(drupal_get_user_timezone());
}

/**
 * Forcefully starts a session, preserving already set session data.
 *
 * @ingroup php_wrappers
 */
function drupal_session_start() {
	// Command line clients do not support cookies nor sessions.
	if (!drupal_session_started() && !drupal_is_cli()) {
		// Save current session data before starting it, as PHP will destroy it.
		$session_data = isset($_SESSION) ? $_SESSION : NULL;

		session_start();
		drupal_session_started(TRUE);

		// Restore session data.
		if (!empty($session_data)) {
			$_SESSION += $session_data;
		}
	}
}

/**
 * Commits the current session, if necessary.
 *
 * If an anonymous user already have an empty session, destroy it.
 */
function drupal_session_commit() {
	global $user;

	if (!drupal_save_session()) {
		// We don't have anything to do if we are not allowed to save the session.
		return;
	}

	if (empty($user->uid) && empty($_SESSION)) {
		// There is no session data to store, destroy the session if it was
		// previously started.
		if (drupal_session_started()) {
			session_destroy();
		}
	}
	else {
		// There is session data to store. Start the session if it is not already
		// started.
		if (!drupal_session_started()) {
			drupal_session_start();
		}
		// Write the session data.
		session_write_close();
	}
}

/**
 * Returns whether a session has been started.
 */
function drupal_session_started($set = NULL) {
	static $session_started = FALSE;
	if (isset($set)) {
		$session_started = $set;
	}
	return $session_started && session_id();
}

/**
 * Called when an anonymous user becomes authenticated or vice-versa.
 *
 * @ingroup php_wrappers
 */
function drupal_session_regenerate() {
	global $user, $is_https;
	if ($is_https && variable_get('https', FALSE)) {
		$insecure_session_name = substr(session_name(), 1);
		if (isset($_COOKIE[$insecure_session_name])) {
			$old_insecure_session_id = $_COOKIE[$insecure_session_name];
		}
		$params = session_get_cookie_params();
		$session_id = drupal_hash_base64(uniqid(mt_rand(), TRUE) . drupal_random_bytes(55));
		// If a session cookie lifetime is set, the session will expire
		// $params['lifetime'] seconds from the current request. If it is not set,
		// it will expire when the browser is closed.
		$expire = $params['lifetime'] ? REQUEST_TIME + $params['lifetime'] : 0;
		setcookie($insecure_session_name, $session_id, $expire, $params['path'], $params['domain'], FALSE, $params['httponly']);
		$_COOKIE[$insecure_session_name] = $session_id;
	}

	if (drupal_session_started()) {
		$old_session_id = session_id();
	}
	session_id(drupal_hash_base64(uniqid(mt_rand(), TRUE) . drupal_random_bytes(55)));

	if (isset($old_session_id)) {
		$params = session_get_cookie_params();
		$expire = $params['lifetime'] ? REQUEST_TIME + $params['lifetime'] : 0;
		setcookie(session_name(), session_id(), $expire, $params['path'], $params['domain'], $params['secure'], $params['httponly']);
		$fields = array('sid' => session_id());
		if ($is_https) {
			$fields['ssid'] = session_id();
			// If the "secure pages" setting is enabled, use the newly-created
			// insecure session identifier as the regenerated sid.
			if (variable_get('https', FALSE)) {
				$fields['sid'] = $session_id;
			}
		}
		db_update('sessions')
		->fields($fields)
		->condition($is_https ? 'ssid' : 'sid', $old_session_id)
		->execute();
	}
	elseif (isset($old_insecure_session_id)) {
		// If logging in to the secure site, and there was no active session on the
		// secure site but a session was active on the insecure site, update the
		// insecure session with the new session identifiers.
		db_update('sessions')
		->fields(array('sid' => $session_id, 'ssid' => session_id()))
		->condition('sid', $old_insecure_session_id)
		->execute();
	}
	else {
		// Start the session when it doesn't exist yet.
		// Preserve the logged in user, as it will be reset to anonymous
		// by _drupal_session_read.
		$account = $user;
		drupal_session_start();
		$user = $account;
	}
	date_default_timezone_set(drupal_get_user_timezone());
}

/**
 * Session handler assigned by session_set_save_handler().
 *
 * Cleans up a specific session.
 *
 * @param $sid
 *   Session ID.
 */
function _drupal_session_destroy($sid) {
	global $user, $is_https;

	// Delete session data.
	db_delete('sessions')
	->condition($is_https ? 'ssid' : 'sid', $sid)
	->execute();

	// Reset $_SESSION and $user to prevent a new session from being started
	// in drupal_session_commit().
	$_SESSION = array();
	$user = drupal_anonymous_user();

	// Unset the session cookies.
	_drupal_session_delete_cookie(session_name());
	if ($is_https) {
		_drupal_session_delete_cookie(substr(session_name(), 1), TRUE);
	}
}

/**
 * Deletes the session cookie.
 *
 * @param $name
 *   Name of session cookie to delete.
 * @param $force_insecure
 *   Force cookie to be insecure.
 */
function _drupal_session_delete_cookie($name, $force_insecure = FALSE) {
	if (isset($_COOKIE[$name])) {
		$params = session_get_cookie_params();
		setcookie($name, '', REQUEST_TIME - 3600, $params['path'], $params['domain'], !$force_insecure && $params['secure'], $params['httponly']);
		unset($_COOKIE[$name]);
	}
}

/**
 * Ends a specific user's session(s).
 *
 * @param $uid
 *   User ID.
 */
function drupal_session_destroy_uid($uid) {
	db_delete('sessions')
	->condition('uid', $uid)
	->execute();
}

/**
 * Session handler assigned by session_set_save_handler().
 *
 * Cleans up stalled sessions.
 *
 * @param $lifetime
 *   The value of session.gc_maxlifetime, passed by PHP.
 *   Sessions not updated for more than $lifetime seconds will be removed.
 */
function _drupal_session_garbage_collection($lifetime) {
	// Be sure to adjust 'php_value session.gc_maxlifetime' to a large enough
	// value. For example, if you want user sessions to stay in your database
	// for three weeks before deleting them, you need to set gc_maxlifetime
	// to '1814400'. At that value, only after a user doesn't log in after
	// three weeks (1814400 seconds) will his/her session be removed.
	db_delete('sessions')
	->condition('timestamp', REQUEST_TIME - $lifetime, '<')
	->execute();
	return TRUE;
}

/**
 * Determines whether to save session data of the current request.
 *
 * This function allows the caller to temporarily disable writing of
 * session data, should the request end while performing potentially
 * dangerous operations, such as manipulating the global $user object.
 * See http://drupal.org/node/218104 for usage.
 *
 * @param $status
 *   Disables writing of session data when FALSE, (re-)enables
 *   writing when TRUE.
 *
 * @return
 *   FALSE if writing session data has been disabled. Otherwise, TRUE.
 */
function drupal_save_session($status = NULL) {
	$save_session = &drupal_static(__FUNCTION__, TRUE);
	if (isset($status)) {
		$save_session = $status;
	}
	return $save_session;
}
